1. Field of the Invention
The subject of the present invention is an electrochemical device, especially an electrically controllable system of the glazing type and with variable energy and/or optical properties or a photovoltaic device.
2. Discussion of the Background
At the present time, there is an increased demand for glazing called “intelligent” glazing capable of being adapted to the needs of the users.
There is also an increased demand for photovoltaic glazing, which makes it possible to convert solar energy into electrical energy.
With regard to “intelligent” glazing, this may involve controlling the amount of sun passing through glazing mounted externally in buildings or vehicles of the automobile, train or aircraft type. The aim is to enable excessive heating inside passenger compartments or premises to be limited, but only in the case of strong sunshine.
It may also involve controlling the degree of vision through glazing, especially so as to cloud them, make them diffusing or even to prevent any vision when that is desirable. This may relate to glazing mounted as interior partitions in premises, trains, aircraft or mounted in the side walls of an automobile. This also relates to mirrors used as rear-view mirrors, in order to promptly prevent the driver getting dazzled, or signaling panels, in order that messages appear when this is necessary, or intermittently in order to attract attention better. Glazing which can be made diffusing at will can be used when desired as projection screens.
There are various electrically controllable systems which make this sort of modification in appearance or thermal properties possible.
To modify the light transmission or the light absorption of the glazing, there are systems called viologen systems, such as those described in patents U.S. Pat. No. 5,239,406 and EP-612 826.
To modify the light transmission and/or the thermal transmission of the glazing, there are also systems called electrochromic systems. These generally comprise, in a known manner, two layers of electrochromic material separated by an electrolyte layer and surrounded by two electroconductive layers. Each of these layers of electrochromic material may reversibly insert cations and electrons, the alteration of their oxidation state following these insertions/deinsertions leading to an alteration in their optical and/or thermal properties.
It is common practice to put the electrochromic systems into three categories:                that where the electrolyte is in the form of a polymer or a gel; for example, a proton conductive polymer such as those described in patents EP-253 713 or EP-670 346 or a lithium-ion-conducting polymer such as those described in patents EP-382 623, EP-518 754 and EP-532 408, the other layers of the system generally being mineral in nature,        that where the electrolyte is mainly a mineral layer. This category is often called an “all-solid” system, examples thereof can be found in the patents EP-867 752, EP-831 360, the patent FR-99/03420 filed on Mar. 19, 1999 corresponding to patent PCT/FR00/00675 filed on Mar. 17, 2000, the patent FR-2 781 084 corresponding to the patent of filing number WO/FR99/01653, filed on Jul. 8, 1999,        that where all the layers are polymer-based, a category which is often called an “all-polymer” system.        
There are also systems called “light valve” systems. These involve films comprising a polymer matrix which is generally crosslinked, in which microdroplets, containing particles which are capable of placing themselves in a favored direction under the action of a magnetic or electric field, are dispersed. A light valve comprising a polyorganosilane matrix and particles of the polyiodide type, which intercept much less light when a voltage is applied to the film, is also known from patent WO93/09460.
Systems called liquid crystal systems may also be mentioned, with a mode of operation similar to the above. They are based on the use of a polymer-based film placed between two conductive layers, in which droplets of liquid crystals, in particular nematic liquid crystals with positive dielectric anisotropy, are arranged. When a voltage is applied to the film, the liquid crystals orient themselves along a favored axis, which enables vision. Without the voltage, in the absence of crystal alignment, the film becomes diffusing and prevents vision. Examples of such films are described, in particular, in European patent EP-0 238 164, and American patents U.S. Pat. No. 4,435,047, U.S. Pat. No. 4,806,922, U.S. Pat. No. 4,732,456. This type of film, once interposed and incorporated between two glass substrates, is marketed by Saint-Gobain Glass under the commercial name “Priva-Lite”.
In fact it is possible to use all the liquid crystal devices known under the names of “NCAP” (Nematic Curvilinear Aligned Phase) or “PDLC” (Polymer Dispersed Liquid Crystal).
It is also possible to use, for example, cholesteric liquid crystal polymers, such as those described in patent WO92/19695.
All these systems have in common the need to be equipped with current leads to supply electrodes generally in the form of two electroconductive layers on each side of the layer or various active layer(s) of the system.
These current leads are often in the form of metal clips placed above and below the glazing region provided with the active layer or layers. They are perceived as unesthetic, hence the need to hide them by various means. This masking of the periphery of electrically controllable systems complicates their manufacture and moreover reduces the “active” area of the glazing that can be exploited by the user.